The present invention relates generally to dust collectors of the type employing self-cleaned filter elements for removing foreign particles from air or other gaseous mediums, and particularly to a unique mounting and drive arrangement for the blower and plenum utilized to clean the filter elements in the dust collector.
Dust collectors that employ self-cleaned filters typically include a housing that is divided by a partition plate or wall into a clean air section and a dirty air section, with a plurality of filter elements (e.g. filter bags) depending from the partition plate into the dirty air section so that air with particles entrained therein can be introduced into the dirty air section and passed through the filter elements whereby the entrained particles are collected on the exterior surfaces of the filter elements and the filtered air flows upwardly from the interior of the filters through openings in the partition and into the clean air section for exhaustion therefrom. Obviously, over time the exterior surfaces of the filter elements will accumulate collected particles to the point where insufficient air can pass through the filter, and to avoid this condition, and to avoid having to replace the filter elements every time they reach this condition, virtually all modern industrial dust collectors include some arrangement for periodically cleaning the filter elements. One well-known system for cleaning the filter elements is a so-called reverse air system in which a blower, usually a centrifugal blower, discharges a continuous stream of cleaning air into a cleaning plenum that continuously rotates over the surface of the partition plate so that cleaning air is directed into the openings in the partition plate through nozzles or openings in the rotating plenum.
An earlier reverse air dust collector is disclosed in Barr et al U.S. Pat. No. 3,951,627, in which the drive motor for the blower is fixed near the center of the clean air section of the housing, and a relatively long shaft extends through the wall of the plenum for rotating the blower impeller at speeds of about 3400 r.p.m. The plenum itself is mounted for rotation about the same axis as the impeller, and it extends radially outwardly a considerable distance to cover the entire surface of the partition plate as it rotates thereacross with a slide plate interposed between the plenum and the surface of the partition plate to facilitate movement of the rotating plenum over the somewhat irregular surface of the partition plate. Since the blower impeller is within the confines of the plenum, it was necessary to provide the rotating plenum with a venturi inlet for admitting inlet air to the inlet of the impeller, which created a practical problem in commercial embodiments of the dust collector. More specifically, the long reach and essentially cantilever support for the plenum, and the uneven surface of the partition plate on which it slides, creates wobbling movement of the plenum as it rotated, and this wobbling movement results in the venturi air inlet on the rotating plenum moving toward and away from the inlet of the rotating impeller. If too large a spacing is provided between these two moving elements, excessive turbulence is created in the flow of inlet air through the inlet venturi because of the break in the smooth surface of the inlet venturi and because of possible recirculation of pressurized air in the plenum back through the spacing On the other hand, if these elements are located too close to one another, they will contact one another and create substantial and dangerous heat resulting from the frictional contact between the moving elements, and in some cases the elements would be severely damaged. Additionally, the floating slide plate between the plenum and partition plate would sometimes create jamming of the plenum when the surface of the partition plate became particularly uneven, and the required extended motor shaft is expensive and can create stability problems when the impeller is mounted at the extending end of the shaft.
In an effort to overcome some of the drawbacks of the above-described reverse air dust collector, a more recent model of a reverse air dust collector is provided with a centrifugal blower and its motor that are both mounted at a fixed position within the clean air section of the housing, and the plenum is mounted for rotation over the partition plate. With this arrangement, the outlet of the fixed blower is directed downwardly, and this outlet discharges into the rotating plenum through a 90-degree elbow that is attached to the plenum for rotation therewith and that must be connected to an expensive swivel joint capable of providing a generally air-tight connection between a fixed outlet conduit, the blower and the rotating inlet of the elbow. Also, the elbow, at its exhaust end, is attached to the plenum through a flexible joint that permits some "play" of the plenum whereby it can ride on the surface of the partition plate during rotation so that the cleaning air discharged from the plenum can pass directly into the filters with a minimum loss of velocity. While reverse air dust collectors of this general type have proved to be satisfactory in operation, the expense involved in providing the aforesaid swivel joint and elbow increases the cost of the apparatus, and the efficiency of the cleaning arrangement is reduced by the fact that the air discharged from the blower must change direction several times before being admitted to the filters.
By the present invention, a reverse air dust collector includes a unique mounting arrangement and drive for the blower, its motor, and the plenum which overcomes the drawbacks discussed above in connection with conventional reverse air dust collectors.